Thực hiện các phép tính sau
a) $2x^{3}$ · ( $3x^{4}$ + $x^{3}$ – $6x^{2}$ + 9x – 1 )
b) (12 + 45 ) · ( 23 + 46 )
c) ( x + y ) · ( x + y )
d) ( x – y ) · ( x + y )
e) ( x – y ) · ( x – y )
f) ( 3x + 2 ) · ( 6x – 7 )
Thực hiện các phép tính sau
a) $2x^{3}$ · ( $3x^{4}$ + $x^{3}$ – $6x^{2}$ + 9x – 1 )
b) (12 + 45 ) · ( 23 + 46 )
c) ( x + y ) · ( x + y )
d) ( x – y ) · ( x + y )
e) ( x – y ) · ( x – y )
f) ( 3x + 2 ) · ( 6x – 7 )
$a.2x^3.(3x^4+x^3-6x^2+9x-1) \\=6x^7+2x^6-12x^5+18x^4-2x^3 \\b.(12+45)(23+46) \\=57.69 \\=3933 \\c.(x+y)(x+y) \\=x^2+xy+xy+y^2 \\=x^2+2xy+y^2 \\d.(x-y)(x+y) \\=x^2-xy+xy-y^2 \\=x^2-y^2 \\e.(x-y)(x-y) \\=x^2-xy-xy+y^2 \\=x^2-2xy+y^2 \\f.(3x+2)(6x-7) \\=18x^2+12x-21x-14 \\=18x^2-9x-14$
a) $2x^3.(3x^4+x^3-6x^2+9x-1)$
$=(2x^3.3x^4)+(2x^3.x^3)-(2x^3.6x^2)+(2x^3.9x)-(2x^3.1)$
$=6x^{12}+2x^9-12x^6+18x^4-2x^3$
b) $(12+45).(23+46)$
$=57.69=145521$
c) $(x+y)(x+y)$
$=x(x+y)+y(x+y)$
$=x^2+xy+xy+y^2$
$=x^2+2xy+y^2$
d) $(x-y)(x+y)$
$=(x-y)x+(x-y)y$
$=x^2-xy+xy-y^2$
$=x^2-y^2$
e) $(x-y)(x-y)$
$=x(x-y)-y(x-y)$
$=x^2-xy-xy+y^2$
$=x^2-2xy+y^2$
f) $(3x+2).(6x-7)$
$=3x(6x-7)+2.(6x-7)$
$=18x^2-21+12x-14$
$=18x^2+12x-35$